DESCRIPTION (p rovided by applicant): Current results in the field of fluid resuscitation indicate that data on plasma viscosity may become an integral part of the decision making process on the form and type of volume restitution and blood replacement following severe blood losses. To this end, the viscosity of the fluid to be administered and its effect on the resulting plasma viscosity of the circulating blood is of paramount importance. These considerations are especially relevant to the formulation of conventional plasma expanders and the emergent field of artificial blood replacement fluids. To date, plasma viscosity has been measured by mechanical devices, which are subject to measurement errors (high tolerances), are time-consuming, requires a fairly large amount of fluid and require meticulous cleaning. Molecular rotors are a novel class of fluorescent molecules that show a viscosity-dependent fluorescence quantum yield and thus can be exploited to determine the viscosity of their environment. Based on our published findings, molecular rotors can be successfully used to probe blood plasma viscosity ex-vivo. Herein we propose the development of fluorescent probes optimized for blood plasma viscosity measurements. This new technology for measuring fluid viscosity will allow fast and low sample volume measurements of the viscosity of blood plasma and blood plasma expanders. Once optimized, the viscosity fluorosensors will be attached to a solid optical surface to generate the critical and unique component for the development of solid-bound optical molecular viscometers. We expect that this fundamentally new technology for measuring fluid viscosity will have applications in a broad range of medical diagnostic approaches, which to the present could not be contemplated because of the complexity of existing methods universally based on mechano/hydraulically based machinery. Furthermore, this technology has the potential to be applicable in many other fields where direct real-time monitoring of viscosity during a process is required. In terms of biomedical applications the uniqueness of the technology proposed is that it addresses all the issues that so far have biomedical viscosity measurements impractical. It utilizes small volume samples, of size identical to that necessary for microhematocrit determinations. It measures plasma viscosity. It uses inexpensive, disposable sample tubes, and therefore does not require cleaning of viscometric surfaces and mechanical calibration. It is a technology that requires minimal training and personnel. It is a new measuring method, implemented in an inexpensive and practical system, configured to yield clinically relevant data on plasma viscosity that has been experimentally demonstrated to be critical for predicting survival. It allows testing of large populations with minimal deployment of resources. This technology allows dealing with plasma viscosity as a clinically relevant parameter, and opens a new medical horizon by means of a procedure that is a simple and unequivocal as a hematocrit determination.